Unfairness commonly impacts human economic decision-making. However, whether inequity aversion impairs pro-social decisions and the corresponding neural processes, is poorly understood. Here, we conducted two experiments to investigate whether human gifting behavior and brain activity are affected by inequity aversion. In experiment 1, participants played as a responder in a joint donation game in which they were asked to decide whether or not to accept a donation proposal made by the proposer. In experiment 2, participants played a donation game similar to experiment 1, but the charity projects were classified as high-deservingness and low-deservingness projects. The results in both of two experiments showed that the participants were more likely to reject an unfair donation proposal and the late positivity potential (LPP)/P300 elicited by fair offers was more positive than moderately unfair and highly unfair offers regardless of charity deservingness. Moreover, after principal component analysis, the differences in P300 amplitude between fair and highly unfair conditions were positively correlated with the acceptance rates in experiment 2. Taken together, our study revealed that late positivity (LPP/P300) reflected the evaluation of fairness of proposals, and could predict subsequent pro-social decisions. This study is the first to demonstrate that inequity aversion reduces pro-social motivation to help innocent third party.

中文翻译：

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不公平感会减少对第三方的慈善捐赠：来自行为和电生理数据的证据。

不公平通常会影响人类的经济决策。然而，对不平等厌恶是否会损害亲社会的决定和相应的神经过程知之甚少。在这里，我们进行了两个实验，以研究人类的天赋行为和大脑活动是否受到不平等厌恶的影响。在实验1中，参加者在联合捐赠游戏中扮演响应者的角色，要求他们决定是否接受提议者提出的捐赠提议。在实验2中，参与者玩了类似于实验1的捐赠游戏，但慈善项目被划分为高收益和低收益项目。两个实验的结果均显示，参与者更有可能拒绝不公平的捐赠提议，并且无论是否值得慈善，公平报价所引起的后期积极潜力（LPP）/ P300都比中等不公平和高度不公平报价更为积极。此外，经过主成分分析，公平和高度不公平条件之间的P300幅度差异与实验2的接受率呈正相关。总的来说，我们的研究表明，后期积极性（LPP / P300）反映了对提案公平性的评估，并可以预测随后的亲社会决定。这项研究是第一个证明不公平厌恶降低了亲社会动机以帮助无辜第三方的行为。